Treatment of hydrocarbon oils



Patented 13, 1942 TREATMENT or mnoonanon'orns Ben B. Corson and GeorgeSfMonroe, Chicago,-

Ill., assignors to Universal Oil Products Company, Chicago,,lll., acorporation of Delaware N Drawing.. Application October so, 1939,

Serial No. 301,948

, 1Claim.- (01.196424) This invention relates particularly to thetreatment of hydrocarbon distillates of gasoline boiling range and morespecifically to a method of treatment whereby the sulfur content of suchdistillates may be reduced withoutundesirably affecting other necessaryproperties. In some instances the treatment may improve the quality ofthe oils treated in other. ways than reduc-, ing the sulfur content, Forexample, there may be reductions in actual and potential gum con-' tent,color, and antiknock value.. a

Desulfurization is one of the majorproblems confronting the petroleumindustry since-many crude p'etroleums, particularlythose of a naphthenicor mixed base character, contain such quantities of sulfur that motorfuel made. from .them by. straight distillation without cracking, .andparticularly those made by cracking their heavier distillates andresidua, frequently contain so much sulfur that their use, withoutspecial treatment, is impossiblesince not only do the sulfur compoundsimpart a foul odor which is undesirable from a sales standpoint, but thesulfurous and sulfuric acids formed by oxidation of .the gasolines inthe cylinders of internal combustion engines frequently cause seriouscrank case corrosion, and the sulfur in the unburned gasolines corrodesfeed lines, carburetorparts,

etc. Although the limits of sulfur tolerance have been raised, due -tobetter ventilation of crank ties-of such gasolines, particularlyanti-knock acid-treated stocks. Dsulfuriz'ation by the use of sulfuricacid therefore was found to have, and still has very limitedapplication.

Among the methods which have been tried to efiect selectivedesulfurization of cracked gaso-f lineswithout adversely affecting otherpropervalue due to removal or. co version of unsaturated compounds ofrelati ely high antiknock ilystsgunder moderate temperature and pressurevalue, is hydrogenationin the presence of cataconditions. J Heretofore,attempts to desulfurize cracked distillates by this method havegenerally met with failure because of the fact that the addition ofhydrogen to unsaturated'hydrocarbons apparently proceeded concurrentlyand excessively with the action of hydrogen, on sulphur compounds ofvarious types so that bythe time the sulfur was reduced to the allowablemaxi- I nium by the formation principally of hydrogen sulfide (evolvedas a gas); the antiknock value of the: gasoline has been seriously andperma cases, within the last few'years, there arestill definite limitsto the total sulfur which is allow able in gasolines for use in internalcombustion engines. Y

When the sulfur problem was-first encountered in motor fuels,;along withother problems peculiar to the treatment of cracked gasolines, such asimprovement in color and gum content,

the principal treatment in vogue was with sulfuric acid which wasgenerally highly effective in improving the color and odorof straightrun paraflinic and mixed base. gasolines. But it was found that the useof sulfuric acid was seldom nently impaired by the saturation ofolefinic hydrocarbons- This has been particularly notable in priorattempts to desulfurize gasoline boiling range liquids made by thepolymerization of the I olefins in hydrocarbon gas mixtures 'containingsulfur compounds, since the olefins are readily hydrogenated, and as arule their paraffinic counterparts have lower antiknockvalue. An-

other difliculty in prior attempts to desulfurize Q without serious lossof antiknock value has been the gradual, and sometimes rapid,deterioration 'of hydrogenation catalysts employed due to the formationof sulfides having reduced or no hydrogenating activity. It is withimprovements in desulfurizing sulfur-containing gasolines by means ofhydrogenation that the present invention is concerned. T

In one specific embodiment, the present inventioncomprises a process fordesulfurizing gasolines containing both olefinic hydrocarbons and sulfurcompounds which comprises subjectselective in improving any one propertysuch as color. For example, if color was improved to a desired point,there was frequently large. losses due to solution and ester, formationof olefinic compounds present. Similarly; attempts to desulfurize withsulfuric acid to meet. the usual requirements of 0.10% sulfur causedextremely high losses and the formation of such compounds as sulfonicacids, sulfones, sulfur ethers etc. which-remained dissolved in thegasoline.) and were only partially removed by treatment with alkalis,clay filtration, or rerunning of the ing the vapors of said gasolinesmixed with relatively large amounts of hydrogen to contact "with nickelsulfide catalysts at temperatures within the approximate range of250-450 C. and suiperatmospheric pressure of the order of 300 poundsperisquare inch or higher while using relatively low liquid spacevelocities.

We have found that-when using nickel sulfide catalysts while observingthe conditions of operation specified that cracked gasolines containingboth sulfur compounds and olefins can be desulfurized to an extentsothat they are readily marketable withoutadversely affecting antilmockvalue. As will be shown in'later examples, a relatively large excess ofhydrogen over that necessary for effecting complete hydrogenation of theolefins and removal of sulfur is necessary and if antiknock losses areto be minimized, the degree of olefin hydrogenation 'rnust be stopped ata definite point depending upon the composition of the gasolines treatedin re- 7 10 corporating nickel sulfide with finely divided'supspect tosulphur and olefinic content.

While th scope of the present invention is not to be in any way limitedby the theory expressed, it is considered to be possible that in thepresence of a large excess of hydrogen'and under the other limitingconditions of operation, the rate of desulfurization reaction increasesout of proportion to the rate of olefin hydrogenation reaction so thateffective sulfur removal is accomplished before undesirable olefinhydrogenation has occurred. Other possible factors arethe rate ofhydrogenation of various types of olefins, both normal and isomeric, butthese are' somewhat unpredictable, particularly in the complicatedmixtures in which they occur in cracked gasoline; In some instanceshighly branched olefin hydrocarbons show greater antiknock afterhydrogenation to the corresponding paraiiins although this rule is by nomeans absolute. Relatively low liquid space velocities are preferable ofthe order of 0.5 to 5 depending upon the chemical and physicalcharacteristics of the gasoline treated. It is to be noted that thetemperatures and pressures employed are of moderate order.

It has been found when using nickel sulfide catalysts in desulfurizingsulfur-containing oils by limited hydrogenation reactions that substan-1 hydrogen in a subsequent operating period, and

eventually sulfurized to nickel sulfide by the sulfur in the gasoline.Whatever nickel sulfide is oxidized to sulfate will be reduced tosulfide by I the hydrogen present during -the operating stages.

While itispreferred to start with nickel sul-. fide catalysts inoperating the process. it is comprised within the scope of the inventionto start with nickel whichis gradually sulfurized during the process ordeliberately sulfurized prior to the inception of the process by passinghydrogen sulfide or some other decomposable sulfur compound, eitherinorganic or organic, through the granular material. The catalyticsulfide may be employed on carriers or spacing agents of a relativelyinert andusually siliceous refractory 7 character. Besides frequentlyused siliceous carrying materials such as diatomaceous earth, clays,'bentonites, montmorillonites', both raw and acid treated, crushedreiract0ries, etc.,' other carriers such as properly prepared alumina,chm-- mium oxide, titanium oxide, cerium oxide, thorium oxide, andzirconium pxide, and even high melting salts such as calcium phosphate,aluminum phosphate, etc. may be used.

A convenient metho of preparing suitable cat.-

or carbonate on a support suspended in a solution of a nickel salt towhich a precipitant is added,- the deposited compound being laterreduced to nickel which is then sulfurized, or the hydroxide orcarbonate, etc. may be directly sulfurized without intermediatereduction. It is also comprised within the scope of the invention toform catalysts by precipitating nickel sulfide directly upon suitablegranular supports or by inand these composites sulfurized by anynecessary method to produce a usable catalyst. 1

.A convenient method of preparing a nickel sulfide catalyst for useaccording to the present, process consists in producing an extremelyactive reduced nickel catalyst supported on inert carrying material inpelleted form, the metal being sulfurized by the use of hydrogen sulfidor sulfur-containing hydrocarbon vapors.

The general method of preparation of such a 5 catalyst involves thefollowing steps: Kieselguhr is suspended in a relatively dilute aqueoussolution of nickel sulfate and a'saturated hot solution of sodiumcarbonate is added gradually with constant agitation, the proportions ofkieselguhr, nickel sulfate, and sodium carbonate being chosen so thatafter washing anddrying the precipitate, pelleting with graphitand'reducing 'with hydrogen, an approximate composition corresponding tothat given below is 5 obtained.

. Per cent Total nickel- 62.0 Oxygen in nickel oxide (NiO) 4.0 Graphite8.0

40 Kieselguhr 28.0

It is only necessary to employ commercially pure sodium carbonate andnickel sulfate in the primaryprecipitation, although for best resultsthe reactions are brought about in distilled water which can be obtainedby the condensation of ordinary plant system. As a rul a considerableexcess of sodium carbonate is employed corresponding to approximately1.7 moles to 1 mole of anhydrous nickel sulfate. It is important thatthetemperature of the suspension of kieselguhr. and nickel sulfate solutionbe kept low and therefore the hot saturated sodium carbonate solution isadded gradually so as to prevent a noticeable rise in temperature.

5 The primary precipitate consists of kieselguhr,

nickel carbonateland nickelous hydroxide, the composition of theparticles of the precipitate without the silica corresponding to theapproximate' formula 2NiCoI .7N1(0H)I.7H2Q; It 18 I 9 probable that someof the water in this formula is associatedwith the kieselguhr. Therelative amounts of carbonate, hydroxide,and water will depend to someextent upon the conditions of drying.

Q The dry precipitate may now be mixed with 4% of its .weight ofpowdered graphite or other suitable lubricant and pelleted into smallcylindrical forms of approximately 4 diameter and b %"-.thickness in,any standard type of pelleting aiysts consistsin prec pitating nickelhydroxide catalyti tivity of the pellets. The approxidata presented. I

mate. composition of the-materialat this point is given below:

The formed pellets which still contain the mixture of carbonate andhydroxide are now heated in a stream of air or nitrogen at a temperatureof approximately 300 0. (572 F.) to eliminate carbon dioxide. -At thistemperature it has been found that there is substantially, no oxidationof the graphite. After the requisite amount of carbonate'decompositionvhas ben effected, the reduction of the nickel oxides isconducted at inuntil a temperature of approximately 425 C.

- (800 F.) is reached, the reduction being con-- tinued untilapproximately 76% of the oxides have been reduced to nickel which givesa material having the composition shown in the second precedingtabulation. Analyses have indicated that in the formation of thecatalyst composite of the preferred composition the following-re- Thefollowing tabulation shows the results obtained in a run made todetermine the degree of olefin hydrogenation which could be toleratedbefore appreciable loss in antiknock value occurred.

H-ydrogcnation, percent Octane number Bromine :Jhg. Stir The catalystemployed in the run which furnished the above datawas incompletelysulfuri zed I at the outset of the run and therefore apparently creasingtemperatures in a stream of hydrogen had too high an activity so thatexcessive hydrogenation of the 'oleflns occurred with a correspondingdrop in octane number as shown after the fifth period of operation. Asthe catalyst beactions take place in the decarbonizing and reductionsteps:

In the heating and reduction steps the porosity and hence the contactsurface of the composite catalyst pellets is greatly increased and thecrushing strength of the pellets is reduced to. gapproximately'50'% oftheir original value, this still being suflieiently high enough so thatthe pellets may be used in; beds of reasonable depth in practice withoutcrushing to produce .fines.

' The pelleted material is then sulfurized by passing hydrogen sulfidethereover at a moderate temperature.

In the general operation of the'process, sulfurcontaining gasoline isvaporized, mixed with a relatively large excess ofihydrogen or gaseshaving a high hydrogen content, and the mixture is preheated to atemperature within the. range. previously. specified and passed overgranular nickel sulfide catalyst ata rate determined bytrial to producethe best results. It is to be recognized that each charging stock willrequire -a different combination of operating variables to To illustratethe med results normally obtainable in the operation of.thepresent'process, the following examples are introduced but with out theintention of unduly limiting the scope of the invention in exactcorrespondence with the Exlmrrn I A gasolinewas treated which had beenproduced by catalytically cracking a gas oil distillate from an EastTexas crude oil. Vapors of the gasoline at a temperature of 350 C. (662F.)

' were injectedinto hydrogen at the same temperatureunder. a' pressureof 900 pounds per squareinch and passed over a supported nickel Ysulfide.catalyst at a liquid space velocity of 1.

- Hydrogen consumed by sulfur, it. bL.

Operating conditions:

came more highly sulfurized the octane number in the product wasregained while the sulfur was still being reduced notably. The followingdatav shows the comparison 01' properties of the charging stock and theproduct being produced at the end of the run:

Chg. stock Product Ind. period, oxygen bomb test, minute 55 1, 4440+Copper dish gum, mg./l00 cc, 69 ll .A. S. T. M. in, g/l00 cc. 7 3 Color,Saybo t Yellow 27 Color stability Yellow 19 Doctor test PositiveNegative Desulf urizationj'of California. w gasoline- Exploratory runsTemperature, C 350 350 .350 350 Temperature, C 662 662 662 662 Hydrogenpress., lbsJsq. in. 300 300 900 900 Liquid space velocity per hour. l. 6l. 3 1. 3 l. 2

Bromine number: 4 Original charge 63 63 63 63 Product"; 40 37 25 llSulfur, weight percent: Original charge 1. l7 1. l7 1. l7 1. l7

' Product. 0.25 0.12 0.16 0.06

Hydrogen, cu. itJbbL:

Hydrogen consumed by sulfur 29 33 32 35 Hydrogen consumed by olefin. 171189 278 385 Hydrogen consumed, total 200 222 310 Y 420 Exit hydrogenfrom plant 200 1,535 325 1,860

'f The following tabulation of data summarizes runs using optimumconditions:

Desu lfurization of California cracked gasoline,

usingoptimum conditions as predicted jrom exploratory runs Operatingconditions:

Temperature, C Temperature, F Hydrogen pressure, lbs./

origliiiglui i ggace velocity per our 11 c c: Bromine number L Sulfur,weight, percent Octane number Octane numbcr+l cc. T. E. L1... Octanenumber+3 cc. T. E. L..."

Product:

Liquid yield, vsgiume, percent"; r

Hydrogen:

Hydrogen consumed by olefin, cu. ft. bl Hydrogen consumed, totalcu.ft.lbbl.. Exit hydrogen from plant, on. lt.lbbl.

sewers:

Y 0118 onlo 0B use desuli io 1 urizat n. 52% dccullurizatiou.

nal charge. possibly due to the removal oi suliur compounds which had apro-knock tendency, and/or the selective hydrogenation of olenns whoseparamnic counterparts possess high antiknockvalue. The sulfur-could bereduced to the negligible value of- 0.05% with the loss or 3 octanenumber ('12 to so) with only 67% of olefln nydrogenation; The highsusceptibility of the product to tetraethyl lead was also noticeable. Inthe saturation of 'oleilns and reduction of sulfur to hydrogen sulfide.

We claim as our invention: A catalytic hydrogenation process foreiiecting ,substantial desuliurization ot a gasoline containing botholei'inic hydrocarbons and suliur compounds and hydrogenation of saidolennic hydrocarbons to an extent not materially reducing the anti-knockvalue of said gasoline. said process comprising subjecting vapors ofsaid gasoline to contact-with a nickel sulfide catalyst in the inpresence 0! an amount of hydrogen approximately iourtimes that requiredfor complete hydrogenation 01' said oleflnie hydrocarbons and saidremoval of sulfur and at a temperature of approximately 350' C. under ahydrogen pressure 7 l5 0! approximately 900 lbs. per square inch and atruns given above the hydrogen excess wasapproximately. 4 times' thatrequired ior complete a liquid-space velocity of not less than one andnot more than two.

BEN 8. 0017808. GEORGE S. MONROE.

